New Delhi: Within seconds of lift off, the engine fuel control switches of Air India’s ill-fated Boeing 787-8 plane got switched off, with one of the pilots asking the other why he cut off and the latter responding, saying he did not do so, according to AAIB.
In its 15-page preliminary report on the crash, which happened in around 30 seconds of the plane lifting off, the Aircraft Accident Investigation Bureau (AAIB) said the fuel control switches were switched on later, but the deceleration in one of the engines could not be stopped.
Releasing the report a month after the fatal crash, the AAIB said the aircraft’s air/ground sensors transitioned to air mode, consistent with liftoff at 08:08:39 UTC.
“The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec,” the report said citing the plane’s Enhanced Airborne Flight Recorders (EAFR).
As per the report, the engines N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off.
“In the cockpit voice recording, one of the pilots is heard asking the other why he cut off. The other pilot responded that he did not do so,” it said.
Providing a sequence of the happenings, AAIB said the CCTV footage obtained from the airport showed Ram Air Turbine (RAT) getting deployed during the initial climb immediately after lift off.
“No significant bird activity is observed in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport perimeter wall,” it said.
As per the EAFR, the engine 1 fuel cutoff switch transitioned from CUTOFF to RUN at about 08:08:52 UTC. Thereafter at 08:08:56 UTC, the engine 2 fuel cutoff switch also transitions from CUTOFF to RUN.
“When fuel control switches are moved from CUTOFF to RUN while the aircraft is in flight, each engines full authority dual engine control (FADEC) automatically manages a relight and thrust recovery sequence of ignition and fuel introduction,” the report said.
“The EGT (Exhaust Gas Temperature) was observed to be rising for both engines, indicating relight. engine 1’s core deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to relight but could not arrest core speed deceleration and reintroduced fuel repeatedly to increase core speed acceleration and recovery,” the report said.
The EAFR recording stopped at 08:09:11 UTC (Coordinated Universal Time).
At about 08:09:05 UTC, one of the pilots transmitted ‘MAYDAY MAYDAY MAYDAY’ and when the Air Traffic Controller (ATCO) enquired about the call sign, there was no response but the ATCO observed the aircraft crashing outside the airport boundary and activated the emergency response.
“At 08:14:44 UTC, Crash Fire Tender left the airport premises for Rescue and firefighting. They were joined by Fire and Rescue services of local administration,” the AAIB said.